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P046. Mucosal immune activation in diarrhea-predominant irritable bowel syndrome: comparison with health controls and ulcerative colitis

C.H. Choi1, J.Y. Ahn1, K.H. Lee1, J.W. Kim1, S.K. Chang1, 1Chung-Ang University College of Medicine, Internal Medicine, Seoul, South Korea

Background

Mucosal immune activation is suggested to have a role in the pathogenesis of irritable bowel syndrome (IBS), especially in diarrheal type. We tried to evaluate mast cell and T cell activation in colonic mucosa of diarrhea-predominant IBS (D-IBS) patients in comparison with healthy controls (HCs) and ulcerative colitis (UC).

Methods

Between November 2007 and May 2010, 83 patients with D-IBS satisfying the Rome III criteria, 49 with UC in remission (UCR, n = 28) or mild activity (UCMA, n = 21), and 25 HCs were recruited. In all cases, biopsies were taken from each of ascending colon, transverse colon, descending colon, sigmoid colon and rectum by colonoscopy, and questionnaires, including symptoms and health-related quality of life (HRQOL) were checked. The numbers of mast cells per one high power field and intraepithelial lymphocytes (IELs) and lamina proprial lymphocytes (LPLs) per 300 cells were counted and analyzed by immunohistochemistry with anti-human mast cell tryptase and anti-CD3 antibodies. The relationship between the immune cell counts and symptoms was analyzed in D-IBS group.

Results

Mean values of mucosal mast cells, IELs and LPLs of all colonic segments were significantly increased in the D-IBS (32.4±15.2, 20.0±9.3 and 31.4±16.4, respectively), UCR (28.2±15.2, 23.0±10.9 and 29.9±17.3, respectively) and UCMA (38.2±16.6, 31.2±10.9 and 51.3±27.4, respectively) patients compared to HCs (14.8±6.7, 10.2±8.1 and 19.9±8.7, respectively) (all P values <0.001). The mucosal mast cell and T cell counts were similar between D-IBS and UCR except a few segments of colon. The IELs and LPLs counts were significantly higher in UCMA than in all other patient groups throughout all colonic segments, especially in lamina propria of rectum. Most scores of abdominal symptoms and HRQOL in D-IBS were significantly higher than those in HCs, and similar with UC. However, the symptom severities were not correlated with the immune cell counts in D-IBS patients.

Conclusion

Colonic mucosal immune cells in D-IBS were increased significantly compared to HCs, and similar with those in UCR. The symptoms in D-IBS and UCR might be originated from low grade inflammation in colonic mucosa.